I've seen quite a number of discussions on karma \ kamma in this forum.
I'd like to recommend the following 'thick' book which covers extensively on this topic for those who are keen to have an in-depth understanding on kamma.
"The Workings of Kamma - 2nd Revised Edition"
The author is Ven. Pa Auk Sayadaw who is both a Tipitaka master & a highly-respected meditation teacher. The book contains many references to various Pali suttas & commentaries.
Some excerpts from the book:
"It is volition bhikkhus, that is kamma, I dedare. Having willed, one accomplishes kamma by body, by speech, and by mind."
"Impossible it is, bhikkhus, there is no occasion where bodily bad conduct could produce a desired, pleasant, and agreeable result: no such possibility is known..."
There are also many interesting kamma related stories taken from sutta found toward the end of chapter III.
You can either have a quick read online here:
http://www.tusitainternational.net/workings-of-karma-r2-by-pa-auk-sayadawor download the pdf file from the ebook section
http://www.tusitainternational.net/downloads/ebook/